Alkylation of hydrocarbons



Patented Dec. 24, 1 946 ALKYLATION OF HYDROCARBONS George B. Hatch andErnest F. Pevere, Beacon, Louis A. Clarke, Fishkill, and Frank H.Bruner.

Beacon, N. Y.,

assignors, by mesne assignments,

to The Texas Company, New York, N. Y., a corporation of DelawareOriginal application August 30, 1939, Serial No,

292,582. Divided and this application January 7, 1941, Serial No.373,416

Claims.

This invention relates to the alkylation of hydrocarbons andparticularly to the alkylation of isoparaflins with olefins in thepresence of a liquid or fluid catalyst for production of gasoline, andhas to do particularly with the operation of an alkylation process.

The present application is a division of Serial No. 292,582, filedAugust 30, 1939, for Alkylation of hydrocarbons, now Patent No.2,267,097, dated December 23, 1941.

The invention has to do with an alkylation process wherein olefin andparaffin hydrocarbons are introduced to a reaction vessel and thereinsubjected toalkylation in the presence of a catalyst such asconcentrated sulphuric acid, hy-

* drated borontrifiuoride and other alkylation catalysts, either with orwithout a promoter. According to the invention a mixture of hydrocarbonsand catalyst is continuously withdrawn from one portion of the reactionvessel and recycled to another portion under conditions of high velocityfluid flow so asto impart a high degree of agitation or turbulence tothe fluid contents of the vessel.

Thus, a stream of hydrocarbons and catalyst comprising productsofreaction may be continuously Withdrawn from the top or upper portion ofa vertical reaction vessel and a predetermined portion thereof recycledto. the reaction vessel. That portion not recycled is subjected tosettling so as to stratify and form a hydrocarbon layer and a catalystlayer. The bydrocarbon layer is removed and subjected to such furthertreatment as may be desired, while the catalyst layer is withdrawn andat least a portion thereof also recycled to the reaction vessel.

An important object of the invention involves withdrawing from thebottom or lower portion of the reaction vessel a portion of the liquidcontents and returning this withdrawn liquid in a stream or streamsflowing under high velocity'so as to impart sufficient agitation to thecontents of the reaction vessel in order to'avoid formation ofrelatively stagnant pools of liquid catalyst within the vessel.

In an alkylation process it ,is essential to I achieve this object inorder to realize eflicient use of the catalyst, as well as to avoidcatalyst deterioration, and also in o der to avoid overtreating certainconstituen s and under-treating other constituents of the hydrocarbonsundergoing treatment. a

The invention is of particular application in the alkylation oflow-boiling isoparafllns, such as isobutane or isopen'tane, witholefins, such as 2 Cs and C4 olefins, for the production of highanti-knock gasoline hydrocarbons.--

In carrying out the alkylation treatment in a continuous manner it isusual to'pass the hydrocarbons to a tower or reaction vessel whereinthey are subjected to alkylation whilein contact with .an alkylationcatalyst, such as concentrated sulphuric acid, under predeterminedconditions of temperature and time of reaction,-

conccntration of acid, and ratio of acid to hydro: I

carbons. I 5

The reacted mixture is drawn offin a continuous stream and introducedtoa 'settlingves'sel; where stratification occurs, with the formation ofa hydrocarbon layer comprising alkylated hydrocarbons, as well asunreacted. hydrocarbons, I and an'acid layer comprising usedacid. All ora portion of the used acid may be recycled to the reaction vessel, whilethe hydrocarbon, layer a is subjected either to further contact with thecatalyst in a subsequent stage, or else neutralized and fractionated toremove the unreacted. hydrocarbons, such as isoparaflins, whicharereturned to the system for alkylation with additional olefins. r Aportionof the reacted mixture drawn off from the reaction vessel may berecycled directly to the reaction vessel without subjecting it tosettling, as above described. In such an operation there is a settlingor stratification to occur within thereaction vessel, due to thedifference in specific" gravity between the hydrocarbons and thealkylation catalyst, for example, concentrated sulphuric acid. As aresult; the acid tends -to be' concentrated in the bottom-or lowerportion of 1 the reaction vessel, due to settling. Relatively stagnantpools of acid may-"thus; accumulate within the lower portion of thevessel, and this is undesirable, from the standpoint of realizing themost efiicient use of the catalyst and also the avoidance of eitherunder or o'ver-treatmentof .certain constituents'of the hydrocarbons.

Accordingly, the present invention involves reducing the amount ofsettling and concentration of acid within the reaction vessel by continuf ously removing some of the concentrate from the lower portion of thevessel, mixing with feed hy-f drocarbons and introducing the mixture toanother portion of the vessel in a highlyturbulent. state. It alsoinvolves maintaining efficient agi-,

tation within the vessel. 1 I p v The invention 'will be understood morefully by reference to the figures of the accompanying drawing. 1 i.

tendency for The drawing illustrates, in each figure, a single reactionunit comprising reaction and settling vessels, although it iscontemplated that a plurality of such stages may be employed, using ineach stage the method or methods of recycling described herein.

As indicated in Fig. 1, the reaction vessel comprises a tower andwherein the olefin and isoparafiln hydrocarbons are subjected to contactwith a catalyst, such as 'concentrated'sulphuric acid. The liquidmixture of unreacted hydrocarbons, alkylate and catalyst, accumulatingin the top ofthe vessel, is continuously drawn ofi through a conduit 2,leading to a settler 3.

The settler 3 is advantageously of conical shape, as indicated, so as tofacilitate removing the separated catalyst from the hydrocarbons asrapidly and as completely as possible and thereby to reduce to a minimumthe time ofcontact between catalyst and hydrocarbons after introductionto the settler.

The conduit 2 contains an orifice or valve 4 adaptedto control theamount of liquid mixture passing to the settler 3. That portion notpassed to the settler 3 is by-passed through a conduit 5, communicatingwith a recycle pump 6. The pump 6 discharges'through nozzles I, which inturn discharge into the bottom of the reaction vessel I.

The feed hydrocarbons, together with recycled isoparaffin hydrocarbons,may be introduced to the suction side of the pump through a pipe 8.

In operation a stream of liquid mixture is continuously withdrawn fromthe lower portion of the reaction vessel I through a pipe 9 containing acontrolled orifice Ill. The pipe 9 communicates with the conduitpreviously mentioned, so that the liquid mixture withdrawn through thepipe 9 is conducted to the suction side of the pump 6 and therecommingled with fresh feed hydrocarbons and recycled isoparaflinhydrocarbons prior to passage through the nozzles into the bottom of thevessel I.

The used catalyst withdrawn from the settler 3 is passed, all or inpart, through a conduit II, also communicating with the suction side ofthe pump 6. Fresh catalyst, added as makeup, may be introduced through apipe l2, communicating with pipe previously mentioned.

The circulating stream of hydrocarbon and catalyst passing through thepump 6 may contain a ratio of catalyst to hydrocarbon of about 1:1 byvolume. Where the catalyst is sulphuric acid the concentration ismaintained in the range of about 90 to 100% H2804.

The ratio of circulated hydrocarbon to fresh feed hydrocarbon ismaintained high and may range between about 5:1 and 100:1, andpreferably between about 10:1 and 30: 1.,

The-orifices 4' and III are regulated so that the recycled hydrocarboncatalyst mixture passing through the pipe 9 is sufilcient to preventformation of a pool of separated catalyst in the lower portion ofthe'reactor; This, of course, depends upon a number of factors,including the efficiency of agitation, catalyst ratio, and nature ofcatalyst. In general, the proportion withdrawn through pipe 9 is lessthan the overflow through pipe 2, and may comprise about,

575% of the latter.

Fig. 2 likewise shows a reaction vessel provided with" an overflow pipe2| through which the mixture of unreacted hydrocarbons, alkylate andcatalyst accumulating in the top of the vessel is drawn off. The pipe 2|is provided with a 4 controlled orifice 22, controlling the proportionof the drawn-off mixture passing to a settler 23, similar to the settler3 described in connection with Fig. 1.

That portion of the withdrawn mixture not passing to the settler 23flows through a pipe 24 communicating with the suction side of a pump 25and by which means it is reintroduced to the I lower portion of thereaction vessel 20.

Catalyst with some hydrocarbon accumulating in the bottom of thereaction vessel 20 is withdrawn through line 26 by a pump 21, whichdischarges this liquid through a nozzle or nozzles 28, discharging intothe upper portion of the reaction vessel 20.

Feed hydrocarbons, together with recycled isoparafiin hydrocarbons, areintroduced to the suction side of the pump 21 through a pipe 29. Usedcatalyst, withdrawn from the bottom of the settler 23, together with anymakeup catalyst, is conducted by a pipe 3|! communicating with the pipe26, leading to the suction side of the pump 21.

Thus, one feature of the method of flow 11- lustrated in Fig. 2 involvesthe realizing of countercurrent flow within the vessel between therecycled liquid discharged through the nozzles 28 and the recycledliquid introduced to the lower portion of the vessel by the pump 25.

In Fig. 3, fresh feed from line 39, recycle catalyst from line 35, freshcatalyst from line 31, and catalyst-hydrocarbon mix from line 38 aremixed and forced by pump 36 through mixing nozzles 40 into reaction tube4|, which discharges into the upper portion of secondary reaction vessel3|. A controlled proportion of reaction products is continuouslywithdrawn from an intermediate point of vessel 3| by line 32 containingorifice 33. Pipe 32 preferably discharges from vessel 3| at a pointvarying from about onehalf to three-quarters of the height of thevessel.

The withdrawn liquid is passed to a separator 34, by which means thehydrocarbons are separated from the used catalyst. The used catalyst,

all or in part, is returned by pipe 35 to the suction side of arecycling pump 36.

The suction side of the pump 36 also communicates through a pipe 38,with the bottom of the reaction vessel 3|, thereby drawing off suchportion as may be desired of the liquid mixture accumulating in thebottom of the vessel.

The recycled hydrocarbons, feed hydrocarbons, and the recycled catalyst,together with makeup catalyst, etc., are brought into intimate contactby pump 36 and forced through nozzles 40,. as

previously described, into tube 4|, which is a relatively long conduitof restricted crosssectional area, and therefore adapted to prolong theefiect of agitation and turbulent flow as the fluid discharged throughthe nozzles 40 rises therethrough.

A certain amount of settling is permitted in the reaction vessel 3| soas to permit drawing off a stream rich in hydrocarbons through the pipe32, while recycling through the pipe 38 a mixture richer in catalyst.

While single stage operations have been illustrated in the drawing, itis contemplated that the methods of flow described may be used formultiple stage operations and, in which case, the feed hydrocarbons maybe introduced in part to each stage or to as many of the stages as maybe desired.

Obviously many modifications and variations of the invention, ashereinbefore set forth, may

, 'zone flows and wherein partial settling of be made without departingfrom the spirit and scope thereof, be imposed as are indicated in theappended claims.

We claim:

1. In the continuous alkylation of an isoparafiin with an olefin in thepresence of an immiscible alkylation catalyst of greater density thanthe hydrocarbons undergoing treatment, wherein the feed hydrocarbons arecontinuously introduced into a closed circuit containing recirculatingemulsion of mixed catalyst and hydrocarbons undergoing reaction andconstituting an alkylation reaction zone, and a portion of therecirculating emulsion stream is continuously diverted to a separatingzone where catalyst phase is settled from hydrocarbon phase and bothphases are continuously discharged from the separating zone, and atleast a portion of the eparated catalyst phase is recycled to the alklation reaction zone, the improvement which comprises removing theseparated catalyst from the separating zone as rapidly and completely aspossible to thereby reduce to a minimum the timeof contact betweencatalyst and hydrocarbon after separation from the emulsion. I

2. In the continuous alkylation of an isoparafiin with an olefin in thepresence of strong sulfuric acid of about 90-100% strength, wherein thefeed hydrocarbons are continuously introduced on the suction side of arecirculating pump into a flowing stream of emulsion of mixed acid andhydrocarbons undergoing reaction, the flowing stream is forced withturbulent flow through a restricted flow passage under alkylatingconditions, and the mixture then passes through an enlarged flowpassage, from which a portion of the acid and hydrocarbons is returnedto the suction side of the pump for recirculation through the system anda portion of the acidand hydrocarbons is diverted to a settling zonewhere acid is settled from hydrocarbons, and'settled acid is withdrawnfrom said settling zone and at least a portion and only such limitationsshould I s-a tling zone where remaining catalyst is settled while thestream of mixture richer in hifdrocar a I bons is withdrawn from anintermediate portion thereof.

6. The method according to claim 3, wherein the remaining catalystsettled from hydrocarbons in said second settling zone is separated fromthe hydrocarbons as rapidly and completely as possible to thereby reduceto a minimum the time of contact between catalyst and hydrocarbonsthereof is recycled to the recirculating emulsion stream, theimprovement which comprises removing the settled acid from the settlingzone as rapidly and as completely as possible to thereby reduce to aminimum the time of contact between acid and hydrocarbons afterseparation from the emulsion.

3. In the continuous alkylation of a low-boiling isoparafiin with anolefin in the presence of an immiscible alkylation catalyst of greaterdensity than the hydrocarbons undergoing treatment, the

process which comprises maintaining two zones of reaction in series, thefirst of which comprises an initial zone of reaction wherein feedhydrocarbons are introduced into a flowing stream of emulsion of mixedcatalyst and hydrocarbons undergoing reaction and the mixture isagitated under alkylating conditions, and the second of which comprisesa secondary relatively quiescent reaction zone into which emulsion fromthe first the emulsion occurs forming a lower mixture richer in catalystand an upper mixture richer in hydrocarbons, continuously recycling fromthe said second zone a 'stream of the mixture which has only partiallysettled and which is richer in catalyst but which has not formed asettled catalyst layer to the said ,first reaction zone to provide thesaid flowing stream of emulsion therein, and continuously withdrawingzone a stream of the mixture richer in hydrocarbons and passing saidstream to from the said second a second setafter separation from theemulsion.

7. In the continuous alkylation of a low-boiling isoparaflin with anolefin in the presence of an immiscible alkylation catalyst of greaterdensity than the hydrocarbons undergoing treatment, the process whichcomprises continuously feeding the hydrocarbons into a mixed catalystand hydrocarbons undergoing reaction, passing the flowing stream througha restricted flow passage with turbulent flow under alkylatingconditions, then introducing the stream into the upper portion of anenlarged secondary reaction chamber providing relatively quiescent flowwhere additional reaction time is provided and partial settling ofcatalyst from hydrocarbons occurs to form a lower mixture richer incatalyst and an upper mixture richer in hydrocar bons, continuouslyrecycling from said enlarged chamber a stream of the mixture which hasonly partially settled and which is richer in catalyst but which has notformeda settled catalyst layer tothe said restricted fiow passage toform the flowing emulsion stream into which the feed hydrocarbons areintroduced, and continuously diverting from an intermediate portion ofsaid enlarged chamber a stream of the mixture richer in hydrocarbons andpassing said stream to a quiescent settling zone where remainingcatalyst from the hydrocarbons.

separates 8. In an alkylation process in which an emulsion of reactivehydrocarbons and strong mineral acid is maintained and circulated in acirculatory system comprising a reaction zone and a primary settlingzone, the improved method which comprises partially settling theemulsion entering said primary settling zone to form an upper layer ofemulsion which is rich in hydrocarbons and a lower layer ofemulsion'which is richer in acid, recycling the said lower layer ofemulsion to the reaction zone before a settled acid layer has formedtherefrom, separately withdrawing the said upper layer of emulsion fromthe said pri-' mary settling zone and diverting the same to a secondarysettling zone wherein substantially complete separation of acid fromhydrocarbons is effected; i

9. In the continuous alkylation of a low-boiling isoparaflin with anolefin inthe presence of an acid alkylation catalyst of greater densitythan the hydrocarbons undergoing, treatment, the process which comprisesmaintaining two zones in series, the first of which comprises anrinitialzone of reaction wherein feed hydrocarbons are introfiowing emulsionstream ofduced into a flowing stream of emulsion of mixed catalyst andhydrocarbons undergoing reaction and the mixture is agitated underalkylating conditions, and the second of which comprises a, secondaryreaction zone into which emulsion from the first zone flows and whereinpartial settling of the emulsion occurs, forming a lower emulsion richerin catalyst and an upper emulsion richer in hydrocarbons, continuouslyrecycling a stream of the emulsion richer in catalyst before the samehas separated into a settled acid catalyst layer from the said secondzone to the said initial reaction zone to provide the said flowingstream of emulsion therein, and continuously withdrawing from the saidsecondary'reaction zone a stream of the emulsion richer in hydrocarbonsand passing said stream to a settling zone where remaining catalyst issettled from hydrocarbons.

10. Process for the continuous alkylation of an isoparaiiin with anolefin in the presence of alkylation catalyst which comprisesmaintaining zones of agitated reaction, partial settling and morecomplete settling in series; continuously feeding the isoparaffln andolefin into the agitated reaction zone containing an emulsion ofhydrocarbons and alkylation catalyst under alkylating conditions,passing emulsion from said reaction zone to the partial settling zonewhere incomplete settling of emulsion occurs, recycling partially butincompletely settled emulsion from one elevation of said partialsettling zone to said reaction zone before the said emulsion hasseparated into a settled catalyst layer, passing additional emulsionfrom a different and higher elevation of said partial settling zone tosaid more complete settling zone where a separate hydrocarbon phase isformed, and recovering alkylate from said hydrocarbon phase.

GEORGE B. HATCH. ERNEST F. PEVERE. LOUIS A. CLARKE. FRANK H. BRUNER.

